The present invention relates to a super high vacuum vessel suitable for achieving therein a super high vacuum pressure and its sealing structure, for example, a vacuum pressure exceeding 10.sup.-10 Torr or 10.sup.-11 Torr using a relatively simple evacuation system.
Japanese Patent application First Publications Hesei 1-316439, Heisei 3-31451, Showa 60-36648, Showa 59-153514, Showa 59-183926, Showa 60-128258, Showa 63-12858, and Showa 63-103073 and Japanese Report (Vacuum Volume 341 (1991) page 56, exemplify a raw material composition of a super high vacuum vessel to achieve a high vacuum or super high vacuum pressure.
If a stainless steel is used for a member constituting the vacuum vessel, it is difficult to obtain the vacuum pressure exceeding 10.sup.-11 Torr by evacuation using a turbo pump which is relatively simple in construction. A very complex evacuation system, for example, a titanium sublimation pump or cryopump, is required to achieve the high vacuum pressure exceeding 10.sup.-11 Torr.
Furthermore, the vacuum vessel made of a super purified steel or stainless steel is very heavy. If an Aluminum alloy is used, it is very difficult to achieve the super high vacuum pressure exceeding 10.sup.-11 Torr, since the gas discharge quantity from the vacuum vessel is large although the total weight thereof is light. If stainless steel is used as the raw material of the vacuum vessel, gas is discharged from the stainless steel so that an electrolytic polishing on an inner surface of the vacuum vessel or a super purified steel with extremely reduced impurities are required in order to obtain a super high vacuum pressure exceeding 10.sup.-11 Torr. In addition, a very complex evacuation system, such as an ion pump, titanium supplemation pump, or cryopump, is needed.
Recently, experimental use of a super high vacuum vessel in cosmic space was contemplated. In this case, the weight of the vacuum vessel material becomes critical. Stainless steel or super purified steel, is extremely heavy.
It is not easy to achieve the super high vacuum pressure exceeding 10.sup.-11 Torr, since an aluminum alloy provides a large gas discharge quantity, although it can be used as a light-weight vacuum vessel material.